Merge pull request #588 from paulkaplan/sound-editor--effects-backend

package.json

src/containers/sound-editor.jsx

src/lib/audio/audio-effects.js

src/lib/audio/effects/echo-effect.js

src/lib/audio/effects/robot-effect.js

src/lib/audio/effects/volume-effect.js

test/__mocks__/audio-effects.js

test/unit/containers/sound-editor.test.jsx

test/unit/util/audio-effects.test.js